Estimation of cardiac output in patients with congestive heart failure by analysis of right ventricular pressure waveforms

<p>Abstract</p> <p>Background</p> <p>Cardiac output (CO) is an important determinant of the hemodynamic state in patients with congestive heart failure (CHF). We tested the hypothesis that CO can be estimated from the right ventricular (RV) pressure waveform in CHF patients using a pulse contour cardiac output algorithm that considers constant but patient specific RV outflow tract characteristic impedance.</p> <p>Method</p> <p>In 12 patients with CHF, breath-by-breath Fick CO and RV pressure waveforms were recorded utilizing an implantable hemodynamic monitor during a bicycle exercise protocol. These data were analyzed retrospectively to assess changes in characteristic impedance of the RV outflow tract during exercise. Four patients that were implanted with an implantable cardiac defibrillator (ICD) implementing the algorithm were studied prospectively. During a two staged sub-maximal bicycle exercise test conducted at 4 and 16 weeks of implant, COs measured by direct Fick technique and estimated by the ICD were recorded and compared.</p> <p>Results</p> <p>At rest the total pulmonary arterial resistance and the characteristic impedance were 675 ± 345 and 48 ± 18 dyn.s.cm^-5, respectively. During sub-maximal exercise, the total pulmonary arterial resistance decreased (Δ 91 ± 159 dyn.s.cm^-5, p < 0.05) but the characteristic impedance was unaffected (Δ 3 ± 9 dyn.s.cm^-5, NS). The algorithm derived cardiac output estimates correlated with Fick CO (7.6 ± 2.5 L/min, R²= 0.92) with a limit of agreement of 1.7 L/min and tracked changes in Fick CO (R²= 0.73).</p> <p>Conclusions</p> <p>The analysis of right ventricular pressure waveforms continuously recorded by an implantable hemodynamic monitor provides an estimate of CO and may prove useful in guiding treatment in patients with CHF.</p

The management of heart failure in Sweden—the physician’s perspective: a survey

AimsTo assess the barriers to guideline-directed medical therapy (GDMT) use in heart failure (HF), diagnostic workup and general knowledge about HF among physicians in Sweden.MethodsA survey about the management of HF was sent to 828 Swedish physicians including general practitioners (GPs) and specialists during 2021–2022. Answers were reported as percentages and comparisons were made by specialty (GPs vs. specialists).ResultsOne hundred sixty-eight physicians participated in the survey (40% females, median age 43 years; 41% GPs and 59% specialists). Electrocardiography and New York Heart Association class evaluations are mostly performed once a year by GPs (46%) and at every outpatient visit by specialists (40%). Echocardiography is mostly requested if there is clinical deterioration (60%). One-third of participants screen for iron deficiency only if there is anemia. Major obstacles to implementation of different drug classes in HF with reduced ejection fraction are related to side effects, with no significant differences between specialties. Device implantation is deemed appropriate regardless of aetiology (69%) and patient age (86%). Specialists answered correctly to knowledge questions more often than GPs. Eighty-six percent of participants think that GDMT should be implemented as much as possible. Most participants (57%) believe that regular patient assessment in nurse-led HF clinics improve adherence to GDMT.ConclusionObstacles to GDMT implementation according to physicians in Sweden mainly relate to potential side effects, lack of specialist knowledge and organizational aspects. Further efforts should be placed in educational activities and structuring of nurse-led clinics

Quantifying coronary sinus flow and global LV perfusion at 3T

<p>Abstract</p> <p>Background</p> <p>Despite the large availability of 3T MR scanners and the potential of high field imaging, this technical platform has yet to prove its usefulness in the cardiac MR setting, where 1.5T remains the established standard. Global perfusion of the left ventricle, as well as the coronary flow reserve (CFR), can provide relevant diagnostic information, and MR measurements of these parameters may benefit from increased field strength. Quantitative flow measurements in the coronary sinus (CS) provide one method to investigate these parameters. However, the ability of newly developed faster MR sequences to measure coronary flow during a breath-hold at 3T has not been evaluated.</p> <p>Methods</p> <p>The aim of this work was to measure CS flow using segmented phase contrast MR (PC MR) on a clinical 3T MR scanner. Parallel imaging was employed to reduce the total acquisition time. Global LV perfusion was calculated by dividing CS flow with left ventricular (LV) mass. The repeatability of the method was investigated by measuring the flow three times in each of the twelve volunteers. Phantom experiments were performed to investigate potential error sources.</p> <p>Results</p> <p>The average CS flow was determined to 88 ± 33 ml/min and the deduced LV perfusion was 0.60 ± 0.22 ml/min·g, in agreement with published values. The repeatability (1-error) of the three repeated measurements in each subject was on average 84%.</p> <p>Conclusion</p> <p>This work demonstrates that the combination of high field strength (3T), parallel imaging and segmented gradient echo sequences allow for quantification of the CS flow and global perfusion within a breath-hold.</p

Quantification and visualization of cardiovascular 4D velocity mapping accelerated with parallel imaging or k-t BLAST: head to head comparison and validation at 1.5 T and 3 T

<p>Abstract</p> <p>Background</p> <p>Three-dimensional time-resolved (4D) phase-contrast (PC) CMR can visualize and quantify cardiovascular flow but is hampered by long acquisition times. Acceleration with SENSE or k-t BLAST are two possibilities but results on validation are lacking, especially at 3 T. The aim of this study was therefore to validate quantitative in vivo cardiac 4D-acquisitions accelerated with parallel imaging and k-t BLAST at 1.5 T and 3 T with 2D-flow as the reference and to investigate if field strengths and type of acceleration have major effects on intracardiac flow visualization.</p> <p>Methods</p> <p>The local ethical committee approved the study. 13 healthy volunteers were scanned at both 1.5 T and 3 T in random order with 2D-flow of the aorta and main pulmonary artery and two 4D-flow sequences of the heart accelerated with SENSE and k-t BLAST respectively. 2D-image planes were reconstructed at the aortic and pulmonary outflow. Flow curves were calculated and peak flows and stroke volumes (SV) compared to the results from 2D-flow acquisitions. Intra-cardiac flow was visualized using particle tracing and image quality based on the flow patterns of the particles was graded using a four-point scale.</p> <p>Results</p> <p>Good accuracy of SV quantification was found using 3 T 4D-SENSE (r²= 0.86, -0.7 ± 7.6%) and although a larger bias was found on 1.5 T (r²= 0.71, -3.6 ± 14.8%), the difference was not significant (p = 0.46). Accuracy of 4D k-t BLAST for SV was lower (p < 0.01) on 1.5 T (r²= 0.65, -15.6 ± 13.7%) compared to 3 T (r²= 0.64, -4.6 ± 10.0%). Peak flow was lower with 4D-SENSE at both 3 T and 1.5 T compared to 2D-flow (p < 0.01) and even lower with 4D k-t BLAST at both scanners (p < 0.01). Intracardiac flow visualization did not differ between 1.5 T and 3 T (p = 0.09) or between 4D-SENSE or 4D k-t BLAST (p = 0.85).</p> <p>Conclusions</p> <p>The present study showed that quantitative 4D flow accelerated with SENSE has good accuracy at 3 T and compares favourably to 1.5 T. 4D flow accelerated with k-t BLAST underestimate flow velocities and thereby yield too high bias for intra-cardiac quantitative in vivo use at the present time. For intra-cardiac 4D-flow visualization, however, 1.5 T and 3 T as well as SENSE or k-t BLAST can be used with similar quality.</p

Hemodynamic aspects of biventricular pacing in heart failure

Background and aims Biventricular pacing or cardiac resynchronization therapy (CRT) is an established treatment option for selected heart failure (HF) patients. We aimed at evaluating acute and longer-term hemodynamic effects of different pacemaker programmings in CRT patients. For the latter purpose, 10 CRT patients also received an implantable hemodynamic monitor (IHM), allowing for long-term hemodynamic monitoring during ambulatory periods. Study I The hemodynamic effects of varying the atrioventricular delay (AVD) within a clinical relevant range (± 40 ms) were investigated in 27 CRT patients in different body positions and during exercise. Nine patients with 3rd degree AV block, and left ventricular ejection fraction ≥ 45% served as controls. A small but significant reduction in cardiac output (CO) was found when AVD was shortened, while prolongation had no effect. The magnitude of individual CO response to AVD modifications was larger in CRT patients compared with controls, differed substantially between individuals and was associated with left atrial size. Study II We evaluated the accuracy of an algorithm based on pressure waveform characteristics from the IHM to track CO changes. The proposed method (CO IHM) was compared to a non-invasive reference method (inert gas rebreathing, RB) in 12 HF patients. The median inter-patient correlation coefficient (r = 0.83) as well as bias (-0.39 L/min, 11%) and limits of agreements (± 1.57 L/min) were found to be acceptable and appeared favorable compared with 2 clinically accepted methods: Doppler echocardiography and impedance cardiography. CO IHM was subsequently applied in study III and IV for the determination of CO. Study III We investigated the acute hemodynamic effects of different biventricularly paced heart rates (HRs) in 10 CRT patients who had also received an IHM. Increasing the paced HR in the range 60 100 bpm reduced cardiac filling pressures and increased CO. Moreover, a positive force frequency relationship, usually blunted in HF patients, was observed in the right ventricle. Study IV The hemodynamic effects of programming different basic HRs (60 or 80 bpm) were investigated during 2-week periods in a single-blind cross-over study. Hemodynamic data was continuously recorded with the IHM and at the end of each study period patients were assessed by quality of life (QoL), a 6-minute walk test (6MWT) and Brain Natriuretic Peptide (BNP). During pacing at 80 bpm compared with 60 bpm, filling pressures were reduced and CO was increased. However, during the period of pacing at 80 bpm there was a trend of increased filling pressures and stroke volume over time suggestive of a potential gradual deterioration with increased HR. QoL-score, the 6MWT and BNP-levels were unchanged comparing the 2 study periods. Conclusions Varying the AVD within a clinical relevant range in CRT patients has little effect on CO. However, the CO response varies largely between individual patients, suggesting that AVD optimization should be performed routinely not to miss those who may gain a potentially important hemodynamic benefit. A simple IHM algorithm can track CO changes in HF patients with reasonable accuracy. This method was subsequently used to demonstrate beneficial short-term effects of pacing with an elevated HR both at rest and during periods of ambulatory living. Considering the potentially large hemodynamic and clinical effects of differential HR programming in CRT patients, this issue demands further evaluation

Effects of caffeine abstinence on adenosine induced coronary flow reserve quantified on phase contrast velocity encoded MRI of the coronary sinus

Introduction: Adenosine is a common pharmacological vasodilator agent used in first pass perfusion MRI as well as nuclear cardiology and echocardiography. Coronary flow reserve (CFR) by adenosine is inhibited by caffeine and therefore caffeine abstinence is routinely proscribed in patients. However, the guidelines differ regarding how long abstinence is needed from 12 to 24 hours. Purpose: This study was performed to investigate if 12 h caffeine abstinence is enough to provide maximal coronary flow reserve (CFR). Methods: 12 healthy individuals (5 females, 39 ± 14 years) were imaged using a 1.5 T Philips Intera CV at rest and during adenosine infusion (140 μg/kg/min) at two occasions, after 12 and 24 h caffeine abstinence respectively. Coronary sinus flow was measured during breath hold with a phase contrast velocity encoded (PC) TFE sequence with 20 phases per cardiac cycle. Typical imaging parameters were: SENSE factor 2, TE/TR/flip: 3.1/4.8 ms/15°, turbo factor 5, spatial resolution 1.2 × 1.2 × 7 mm and VENC 80 cm/s. CFR was calculated as the ratio between coronary sinus flow/min at adenosine and rest. Cardiac output was measured using PC-MRI of the ascending aorta. Results: CFR was higher (5.4 ± 1.0) at 24 h caffeine abstinence compared to 12 h (4.6 ± 0.8, p = 0.03). In most patients the difference was minimal but in three patients (25%) the increase in CFR at 12 h was less than 30% of that at 24 h caffeine abstinence. The increase in HR did not differ at 24 h (40 ± 7%) and 12 h abstinence (39 ± 5%, p = 0.62) nor did the increase in cardiac output (55 ± 8% vs. 48 ± 8%, p = 0.68). Reported symptoms and the blood pressure reaction did not differ between 24 h and 12 h abstinence, Figure 1. Conclusion: Twelve hours caffeine abstinence results in a lower coronary flow reserve compared to 24 hours and there is a large inter-individual difference to caffeine abstinence. This needs to be taken into consideration when performing adenosine perfusion imaging studies. (Figure Presented)

Cardiovascular dysautonomia in postacute sequelae of SARS-CoV-2 infection

Coronavirus disease 2019 (COVID-19) has led to a worldwide pandemic that continues to transform but will not go away. Cardiovascular dysautonomia in postacute sequelae of severe acute respiratory syndrome coronavirus 2 infection has led to persistent symptoms in a large number of patients. Here, we define the condition and its associated symptoms as well as potential mechanisms responsible. We provide a careful and complete overview of the topic addressing novel studies and a generalized approach to the management of individuals with this complex and potentially debilitating problem. We also discuss future research directions and the important knowledge gaps to be addressed in ongoing and planned studies

Variable velocity encoding in a three-dimensional, three-directional phase contrast sequence: Evaluation in phantom and volunteers.

PURPOSE: To evaluate accuracy and noise properties of a novel time-resolved, three-dimensional, three-directional phase contrast sequence with variable velocity encoding (denoted 4D-vPC) on a 3 Tesla MR system, and to investigate potential benefits and limitations of variable velocity encoding with respect to depicting blood flow patterns. MATERIALS AND METHODS: A 4D PC-MRI sequence was modified to allow variable velocity encoding (VENC) over the cardiac cycle in all three velocity directions independently. 4D-PC sequences with constant and variable VENC were compared in a rotating phantom with respect to measured velocities and noise levels. Additionally, comparison of flow patterns in the ascending aorta was performed in six healthy volunteers. RESULTS: Phantom measurements showed a linear relationship between velocity noise and velocity encoding. 4D-vPC MRI presented lower noise levels than 4D-PC both in phantom and in volunteer measurements, in agreement with theory. Volunteer comparisons revealed more consistent and detailed flow patterns in early diastole for the variable VENC sequences. CONCLUSION: Variable velocity encoding offers reduced noise levels compared with sequences with constant velocity encoding by optimizing the velocity-to-noise ratio (VNR) to the hemodynamic properties of the imaged area. Increased VNR ratios could be beneficial for blood flow visualizations of pathology in the cardiac cycle. J. Magn. Reson. Imaging 2012. © 2012 Wiley Periodicals, Inc

Total heart volume variation throughout the cardiac cycle in man.

Variations in total heart volume (atria plus ventricles) during a cardiac cycle affect efficiency of cardiac pumping. The goals of this study were to confirm the presence, extent, and contributors of total heart volume variation during the cardiac cycle in healthy volunteers with the use of MRI. Eight healthy volunteers were examined by MRI at rest. Changes in total cardiac volume throughout the cardiac cycle were calculated using the following methods: 1) planimetry derived from gradient-echo cine images and 2) flow-sensitive sequences to quantify flow in all vessels leading to and from the heart. The maximum total heart volume diminished during systole by 8.2 +/- 0.8% (SEM, range 4.8-10.6%) measured by method 1 and 8.8 +/- 1.0% (SEM, range 5.6-11.8%) by method 2 with good agreement between the methods [difference according to Bland-Altman analysis -0.6% +/- 1.0% (SD), intraclass correlation coefficient = 0.999]. This decrease in volume is predominantly explained by variation at the midcardiac level at the widest diameter of the heart with a left-sided predominance. In the short axis of the heart, the change of slice volume was proportional to the end-diastolic slice volume. The present study has confirmed the presence of total heart volume variation that predominantly occurs in the region of atrioventricular plane movement and on the left side. The total heart volume variation may relate to the efficiency of energy use by the heart to minimize displacement of surrounding tissue while accounting for the energy required to draw blood into the atria during ventricular systole